1. Field of the Invention
The invention relates to a semiconductor component that can switch from a conducting into a non-conducting state, comprising a doped zone having minority charge carriers, which in the non-conducting state have a given mean bulk lifetime Tau.sub.SRH and thus a mean bulk diffusion length L.sub.D,Bulk and in the conducting state, in which the doped zone is swamped by minority charge carriers in one axial direction, have a shortened lifetime Tau.sub.Aug by virtue of the Auger recombination, and comprising an axially limited region in the doped zone in which recombination centers for reducing the mean bulk lifetime Tau.sub.SRH of the minority charge carriers are present.
2. Discussion of Background
It is known that a reduction in the charge carrier lifetime leads to an improvement in the switching time of a power semiconductor component. A setting of the charge carrier lifetime in a semiconductor component can be achieved with this aim in mind by indiffusion of foreign atoms (e.g. Au or Pt) on the one hand, and by irradiation with protons or electrons, on the other hand. Both the indiffusion of foreign atoms and electron irradiation lead to a relatively homogeneous reduction in lifetime over the entire component. By contrast with the diffusion methods, electron irradiation can, however, be sufficiently well reproduced.
With proton irradiation, a pulse-shaped concentration profile of recombination centers is produced along the current-conducting axis (axial direction). Moreover, the efficiency of the recombination centers can be increased by suitable heat treatment after the irradiation so strongly that overall this method has clear advantages by comparison with Au diffusion (see e.g. "Protonen-bestrahlung von Silizium" ("Proton Irradiation of Silicon"), M. W. Huppi, Diss. ETH No. 8755, pp. 100-110, 1989).
All methods for setting the charge carrier lifetime are inherently subject to the disadvantage that although shorter switching times are achieved by reduction of the charge carrier lifetime, it is necessary to accept in return a higher forward voltage drop (a dissipation in the conducting state). It is known (see e.g. "Shorter Turn-off Times in Insulated Gate Transistors by Proton Implantation", A. Mogro-Campero et al., IEEE Electron Device Letters, Vol. EDL-6, No. 5, May 1985), that with regard to optimizing this trade-off proton irradiation is superior to electron irradiation. This can be explained in terms of the fact that in the case of proton irradiation for setting the lifetime, the degree of freedom in the axial direction of the component (axial lifetime structure) is additionally employed. That is to say, the charge carrier lifetime is reduced only where it is necessary and sensible.